## Quick Reference

A way of denoting a chemical reaction using the symbols for the participating particles (atoms, molecules, ions, etc.); for example,*x*A+*y*B → *z*C+*w*D The single arrow is used for an irreversible reaction; double arrows (⇌) are used for reversible reactions. When reactions involve different phases it is usual to put the phase in brackets after the symbol (s = solid; l = liquid; g = gas; aq = aqueous). The numbers *x*, *y*, *z*, and *w*, showing the relative numbers of molecules reacting, are called the stoichiometric coefficients. The sum of the coefficients of the reactants minus the sum of the coefficients of the products (*x*+*y* – *z* – *w* in the example) is the stoichiometric sum. If this is zero the equation is balanced. Sometimes a generalized chemical equation is considered ν_{1}A_{1}+ν_{2}A_{2}+… → … ν* _{n}*A

_{n}+ν

_{n}_{+1}A

_{n}_{+1}… In this case the reaction can be written Σν

*A*

_{i}*= 0, where the convention is that stoichiometric coefficients are positive for reactants and negative for products. The stoichiometric sum is Σν*

_{i}*.*

_{i}*x*A+*y*B → *z*C+*w*D

ν_{1}A_{1}+ν_{2}A_{2}+… → … ν* _{n}*A

_{n}+ν

_{n}_{+1}A

_{n}_{+1}…

*Subjects:*
Chemistry.